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CVE-2026-68216
media: pwc: Return queued buffers on start_streaming() failure
Published 2026-08-10 (2 months ago) by the Linux kernel CNA. Subsystem drivers/media. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-68216 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | fixedDLA-4777-1 · 2026-09-08 · text | 6.1.187-1 | Update the kernel and reboot. DLA-4777-1 shipped the fix on 2026-09-08, in 6.1.187-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.101-1 | Update the kernel and reboot. Fixed in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The vb2 framework hands buffers to the driver via buf_queue() before calling start_streaming(). If start_streaming() returns an error without first returning those buffers via vb2_buffer_done(), vb2_start_streaming() fires WARN_ON(owned_by_drv_count) and the queued buffers leak. pwc's start_streaming() had two early returns that hit this trap: -ENODEV when the USB device was already disconnected, and -ERESTARTSYS when mutex_lock_interruptible() was interrupted by a signal. Call the existing pwc_cleanup_queued_bufs() helper with VB2_BUF_STATE_QUEUED before returning (matching the state already used by the pwc_isoc_init() error path in the same function). This mirrors the uvcvideo fix in commit 4cf3b6fd54eb ("media: uvcvideo: Return queued buffers on start_streaming() failure").
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/media/usb/pwc/pwc-if.c
- What this is
- PWC WEBCAM DRIVERMAINTAINERS section matched on drivers/media/usb/pwc/* · linux-media@vger.kernel.org · Odd Fixes
- Kernel module
- pwc
Check it on the machine
grep -w CONFIG_USB_PWC /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w pwcPrints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookworm, trixie, forky, sid, bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_USB_PWC
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-08-10 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.18%, higher than 6.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- drivers/media
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 3.5 | 5.10.265 | d552852bf76b |
| 3.5 | 5.15.216 | 0362ae30b61b |
| 3.5 | 6.1.183 | fa78e5908527 |
| 3.5 | 6.6.148 | f2f9fcacd819 |
| 3.5 | 6.12.101 | 5d7cc2634c38 |
| 3.5 | 6.18.42 | cb16b79a2be2 |
| 3.5 | 7.1.6 | a4f8f629983f |
| 3.5 | 7.2 | 975b2ee20e56 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4777-1 | 2026-09-08 | bookworm 6.1.187-1 | tracker |
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The bug is reached through the VIDIOC_STREAMON ioctl on a local V4L2 device node (/dev/videoN) exposed by the pwc USB webcam driver, so the attacker needs local access to the system rather than network reachability.
- AC:LAttack complexity, low
- The -ERESTARTSYS path is triggered deterministically by the attacker: hold pdev->v4l2_lock from a second thread/fd and send a signal to the thread blocked in mutex_lock_interruptible() inside start_streaming(), so both sides of the timing window are attacker-controlled and repeatable.
- PR:LPrivileges required, low
- Only an unprivileged local account with access to the video device node (typical for desktop, kiosk and embedded video appliances, where the video group or logind ACLs grant it) is needed; no capabilities or root are required.
- UI:NUser interaction, none
- The attacker performs the entire sequence (REQBUFS, QBUF, STREAMON, signal delivery) from its own process; no action by any other user is needed.
- S:UScope, unchanged
- The buffer-accounting breakage and the resulting list corruption stay within the kernel's own security authority; no VM, IOMMU or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- Buffers left on pdev->queued_bufs after vb2 has already reclaimed them to QUEUED are re-linked on the next STREAMON, so the same pwc_frame_buf can be filled and completed while vb2 considers it userspace-owned, allowing an attacker to read kernel-managed frame data through stale mmap'ed buffers.
- I:HIntegrity impact, high
- The double list_add_tail() of an already-linked buf->list node corrupts the driver's queued-buffer list and desynchronizes vb2's owned_by_drv_count, giving overlapping kernel/userspace ownership of buffer objects that can be leveraged for controlled modification of kernel-side state.
- A:HAvailability impact, high
- Each attempt fires WARN_ON(owned_by_drv_count) in vb2_start_streaming(), which panics the machine on panic_on_warn kernels, and the leaked/corrupted buffer list additionally leads to lost buffers and unstable streaming state on subsequent STREAMON/STREAMOFF cycles.